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A study of children and their older siblings with autism does not support a link between MMR vaccination and autism spectrum disorders.

While the debate over whether vaccines can cause autism continues, an increasing number of parents are opting out of vaccinating their children, leading to public health issues that have been reported recently in the news. While there are studies that demonstrate no link between vaccinations, in particular, measles-mumps-rubella (MMR) and autism spectrum disorders (ASD), there are still many who oppose vaccinations because of the potential risks.

The MMR vaccine is a single injection that protects against all three diseases. The current vaccination schedule in Canada and the United States calls for MMR immunization between 12-15 months of age, and a second dose at age 4-6 years. Measles infection is characterised by high fever, cough, rash, runny nose, and watery eyes. It can also have serious effects such as ear infections, lung infections, and even encephalitis (an infection in the brain), which can lead to brain damage. Mumps infection causes fever, headache, and swelling of the cheek, jaw, and neck. Mumps infection can also result in meningitis and deafness. Rubella, or German measles, also causes fever, sore throat, and rash. More serious effects of rubella can be inflamed joints, blood clotting, and encephalitis. Measles, mumps, and rubella can cause pregnant women to miscarry or result in premature delivery. Rubella infection during pregnancy can also result in the baby developing congenital rubella syndrome, causing severe disability. All three infections are highly contagious, however, they are easily avoided by immunization.

It is understandable that given the debate over the association between the MMR vaccination and ASD, parents would be wary of vaccinating a younger sibling of a child with ASD. A Canadian study confirms this tendency, demonstrating that younger siblings were less likely to have MMR immunization when they had older siblings with ASD. This study, however, did not find a statistically significant difference between diagnosis of ASD in immunized and non-immunized siblings.

A retrospective study published this month in the Journal of the American Medical Association has aimed to extend these earlier analyses. The study assessed the occurrence of ASD by MMR vaccination status in children who have an older sibling with ASD. A total of 95 727 children with older siblings were included in the analysis. Of these children, just over 1% (994) had a diagnosis of ASD, while just over 2% (1 929) had older siblings who were diagnosed with ASD. Diagnosis of ASD was more prevalent in children who also had older siblings with ASD.

Overall the study reported no association between MMR vaccination and an increase in the risk of ASD. This was true for either 1 or 2 doses of the MMR vaccine. The study finds no evidence of harmful association between MMR vaccination and ASD in younger siblings of children with ASD.


Abu Kuwaik G, Roberts W, Zwaigenbaum L, Bryson S, Smith IM, Szatmari P, Modi BM, Tanel N, Brian J. Immunization uptake in younger siblings of children with autism spectrum disorder.” Autism 2014;18(2):148-155.

Jain, A, Marshall, J, Buikema, A, Bancroft, T, Kelly, JP, newschaffer, CJ. “Autism Occurrence by MMR Vaccine Status Among US Children With Older Siblings With and Without Autism” Journal of the American Medical Association, April 21, 2015, Vol 313, No. 15

Image courtesy of Sura Nualpradid at






Written by Deborah Tallarigo, PhD

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